The value of the mark level cursor reported in Decibel Relative units.

MP

Magnitude Point

The difference between the point and mark levels cursors.

Magnitude Scaling

The normal vertical (i.e. magnitude) resolution of the spectrum analyzer is 10 dB per grid line and precise dB levels can be measured using the spectrum level cursors.

The spectrum magnitude display is unreferenced; all measurements are relative to the prevailing V/Div value on each channel. If you wish to shift the spectrum up to see low level signals simply increase the vertical scale of the associated channel.

However, if you wish to make measurements relative to a standard Decibel scale you can reference the display to show dBu, dBV or dBm values as follows:

Scale

Reference

Calibration

dBu

0.775V (RMS)

Apply a 1 kHz 0.775V (RMS) voltage to any channel via a 1M Ohm (or greater) probe. Mark the peak of the spectral line for 0 dBu.

dBV

1.0V (RMS)

Apply a 1 kHz 1.0V (RMS) voltage to any channel via a 1M Ohm (or greater) probe. Mark the peak of the spectral line for 0 dBV.

dBm

0.224V (RMS)

Apply a 1 kHz 0.224V (RMS) voltage to channel B with 50 Ohm termination enabled. Mark the peak of the spectral line for 0 dBm.

The frequency resolution of the spectrum analyzer depends on the bandwidth (i.e. the prevailing timebase settings) and display sample rate (which depends on display size and mode).

Specifically, choose the SHARPdisplay mode to maximize the frequency resolution for a given display size and maximize the display size. For example the screenshot below was taken from a widened display with a frequency resolution of 2000 bins over 1MHz bandwidth (i.e. 500Hz/bin).

Click the screenshot to see an animated recording of this spectrum (Warning: it's a big file, 12MB).

This recording was created by connecting the flying ground lead of a standard oscilloscope probe to the probe tip, increasing the gain of the BitScope channel and then moving the "loop antenna" thus created near a standard desktop PC.

The signals that can be seen are EMI produced by this equipment. This example demonstrates just how easy it is to use BitScope to check for EMI (e.g. for preliminary EMC testing purposes) even using a simple low gain "antenna" as this.

The bandwidth is reported via the BW parameter and the graticule has 10 vertical divisions, allowing quick frequency measurement to be made in much the same way as time measurements may be made with waveform displays. More precise measurements of spectral features can be made using frequency cursors.